Extramammary Paget disease (EMPD) is a rare skin cancer that affects areas with a high concentration of apocrine glands including genital, axillary, and anal skin. When it affects other locations it is called ectopic extramammary Paget disease (E-EMPD) and is uncommon. To date, there are only 45 case reports to the best of our knowledge. The clinical manifestation is typically a soft, red or bright pink patch or plaque with scattered white islands of hyperkeratosis and erosion. Diagnostic confirmation requires conventional histology with immunohistochemistry. The importance of immunohistochemical staining for the diagnosis of primary neoplasia, without underlying malignancy, is highlighted. We report the first Latin American confirmed case, to our knowledge, of primary E-EMPD in a 55-year-old man with a 1-year history of asymptomatic thoracic plaque.